1. Field of the Invention
The present invention relates to a top chord structure for an open top railcar. More particularly, the present invention relates to a side top chord member, an end top chord member and a corner cap for a top chord structure.
2. Background Information
An open top hopper or gondola-type railcar typically comprises a series of side walls, end walls and vertical posts or side stakes that define the basic perimeter of a container for handling a body of material. The side stakes are spaced along the side walls and are designed to strengthen and reinforce the side walls of the container. End posts or stakes may be spaced along the end walls to strengthen and reinforce the end walls of the container. A top chord structure extends along each of the side walls and end walls of the container to further strengthen and stabilize the walls.
In the handling of material, it is often necessary to subject the top chord structure, in particular the side top chord members, to some high localized forces. For example, in unloading the contents of the railcar into a rotary dumper, it is conventional to clamp the side top chord member as the railcar is tilted or turned into an unloading position. Also, it is conventional to apply a shaker to the top chord structure, in particular the side top chord members, of the railcar to agitate the contents of the railcar during the unloading process. Both such operations impose large localized forces on the top chord structure, specifically the side top chord members.
A typical side top chord member construction is a P-shaped profile. Specifically, the side top chord member is a tubular member having a generally rectangular profile and a stem that is integrally connected with the tubular member. The stem is designed to be bolted to the side wall and the side stakes of the railcar to connect the side top chord member to the railcar.
In the past, railcar designers have recognized the need for special side top chord members to accept these unloading operations. U.S. Pat. Nos. 2,748,723, and 4,561,361 disclose hot rolled steel bulb sections which are especially designed to accommodate rotary car dumpers or car shaker devices. While these rolled bulb sections have proven satisfactory for railcars and side top chord members made of steel, they lack sufficient strength and integrity when used for aluminum railcars and side top chord members. U.S. Pat. No.4,840,127 is an example of a top chord structure designed especially for use in aluminum gondola or hopper cars in which the top chord member is a rectangular, tubular extrusion having a thickened stem portion to better resist bending moments where the side top chord member is fastened to the side walls and side stakes. This top side chord member, while more suitable for aluminum railcars than the rolled bulb section, lacks sufficient strength and integrity for extended use in the rotary or shaker-type car unloading devices. U.S. Pat. No. 5,070,793 (hereinafter xe2x80x9cthe ""793 patent) which is incorporated herein by reference, is an example of a top chord structure designed especially for use in aluminum gondola or hopper cars which is strong, lightweight and suitable for extended use in rotary or shaker-type car unloading devices.
The object of the present invention is to design a side top chord member which maintains the advantages of the ""793 patent and which improves the hauling capacity of the railcar and improves the load carrying capacity of the side top chord member. Another object of the present invention is to design all of the components of the top chord structure to minimize fabrication cost and time and to improve the operating characteristics of the individual components.
The above objects are achieved with a top chord structure according to the present invention. The railcar having the top chord structure according to the present invention includes modified side top chord members which allow for increased hauling capacity. Additionally, the side top chord member is designed to improve the loading characteristics of this member. The end top chord members and corner cap member have been designed to minimize the fabrication and assembly process. The end top chord members have been designed to improve the stress distribution through this member. All of these characteristics combine to form an improved top chord structure for the railcar. These and other advantages of the present invention will be clarified in the description of the preferred embodiments wherein like reference numerals represent like elements throughout.